Question

# The energies of an electron in the first orbit of He+ and in the third orbit of Li2+ in joule are respectively:

A
8.72×1018,2.18×1018
B
8.72×1018,1.96×1017
C
1.96×1017,2.18×1018
D
8.72×1017,1.96×1017

Solution

## The correct option is A −8.72×10−18,−2.18×10−18Energy of an electron in nth orbit  of hydrogen like species =−2.18×10−18Z2n2  where Z is atomic number. For He+→ En=−2.18×10−182212=−8.7×10−18J  For Li2+→ En=−2.18×10−183232=−2.18×10−18J

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